A control lever includes a wheel and a column manipulated by a pilot. The pilot can execute an operating input of a rolling direction (a roll input) by rotating the wheel and an operating input of a pitching direction (a pitch input) by pushing and pulling the column. The roll input and the pitch input are converted into electric signals by displacement sensors of the wheel and column, and are inputted to a fight control computer as a pitch command and a roll command (collectively referred to as an operating command). A control law calculation is executed on the basis of this operating command in the flight control computer and control surfaces are driven by actuators which are controlled based on the calculation result, and thus a fuselage (for example, an aircraft) can be controlled. Japanese Laid-Open Patent Application JP-P 2000-335496 A discloses a flight control system of an aircraft using a fly-by-wire described above.
In the flight control system using the control lever of the wheel and column, the control levers on a pilot side and on a co-pilot side, generally, are mechanically linked and the flight control can be carried out if the input is executed from either one of the control levers. Since a force (an operating input) applied to one of the control levers is transmitted to the other of the control levers by a link mechanism, the two control levers move with being interlocked.
It is assumed that the above described control levers are stuck in a movable portion. When the control levers are stuck, it becomes impossible to carry out the flight control and there is a possibility to lead to a fuselage loss.
In order to avoid the above mentioned uncontrollable state caused by the sticking, a conventional technique includes a mechanism (a separation mechanism) for releasing the mechanical linkage (the link mechanism) between both of the control levers in some way.
As a related technique, there is a flight control system (for example, U.S. Pat. No. 5,782,436) including a mechanism for avoiding the jamming by generating a slip when a force equal to or more than a predetermined value is applied from the control lever to the link mechanism. In this case, even when one of the control levers is jammed, the flight control can be carried out by applying a force equal to or more than the predetermined value to the other non-jammed control lever. However, since a jammed portion is not clear in such a technique, it is required to apply a large force to both of the control levers to specify the operable control lever. In addition, since it is required to generate the slip by applying the force equal to or more than a predetermined value in order to avoid the jamming, a pilot needs to constantly input a large operating force. Furthermore, the technique for avoiding the jamming by using the slip sometimes generates the slip depending on some conditions even in a case other than the jamming. On this occasion, negative effects, such as a false detection of a sensor signal from the control lever and a fighting between systems each of which is connected to both control levers, may sometimes occur.
For this reason, a technique for separating a control lever which is stuck from a non-troubled control lever is demanded.
On the other hand, U.S. Pat. No. 5,456,428 discloses a flight control system for carrying out, when the fly-by-wire is out of order, mechanical backing up by engagement using a clutch.